Vehicular passenger protection system against lateral collision

ABSTRACT

A vehicle has two acceleration sensors, which are provided forward and rearward respectively from the rear end of a driver seat in the vehicle. The acceleration sensors output signals, which are the basis for sensing a signal related to rotation of the vehicle. The sensed signal is the basis for determining whether the vehicle has a lateral collision.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by referenceJapanese Patent Applications No. 2002-272118 filed on Sep. 18, 2002 andNo. 2003-168043 filed on Jun. 12, 2003.

FIELD OF THE INVENTION

The present invention relates to a vehicular passenger protection systemagainst lateral collision that actuates a seat belt, an airbag oranother passenger protecting device of a vehicle in response to alateral collision of a vehicle.

BACKGROUND OF THE INVENTION

JP-A-11-180249 discloses a conventional protection system againstlateral collision that is fit on a vehicle chassis. This protectionsystem has acceleration sensors for sensing the lateral force acting onthe vehicle chassis. If the output from each of the acceleration sensorsexceeds a threshold, the protection system determines that the vehiclehad a lateral collision. This protection system then actuates protectingdevices of the vehicle to protect the passengers in the vehicle. As ageneral rule, a low-frequency component of the output from each of theacceleration sensors is extracted through a low-pass filter or anintegration circuit. The amplitude of the low-frequency component iscompared by a comparison circuit so that malfunctions due tohigh-frequency noises can be suppressed.

In this system, the acceleration sensors are fit to the right and leftside walls of the vehicle chassis as side wall sensors. If anothervehicle collides with one of the side walls, a great impact force actson the associated sensor mounted near the side wall. This sensor thenoutputs a voltage proportional to the impact force. This output voltagetriggers to actuate the airbag or the like installed in the vehiclechassis. Each of the acceleration sensors (side wall sensors) mainlysenses the plastic or elastic deformation of the adjacent side wall dueto a lateral collision of the vehicle chassis. Each sidewall sensor alsosenses the movement of the whole vehicle chassis due to the lateralcollision.

The side wall sensors become less sensitive to the impact force aslocated away from the point on the side wall where the impact forceacts. Accordingly, two such sensors should be fit to a front portion anda rear portion of each of the right and left sidewalls (4 sensors intotal). More preferably, three such sensors should be fit to a frontportion, a middle portion and a rear portion of each side wall (6sensors in total). However, if the driver strongly closes a door of thevehicle, impact force that is not so weak acts on the side wall sensors,which may then cause the airbag or the like to malfunction.

In order to solve this problem, it is proposed that an additionalacceleration sensor be fit in the vehicle dashboard and near the centerof the vehicle, which is less influenced by impact force than the sidewalls when the doors are opened and closed. The impact force developedby a lateral collision of the vehicle is damped and delayed by thedeformation and/or displacement of the vehicle chassis beforetransmitted to this central sensor. Accordingly, by using the outputfrom the central sensor, it is possible to exclude relatively smallimpulses, such as the impulses developed when the doors are closedstrongly, and to sense only the great impulses developed by the lateralcollision. It is also proposed that the central sensor and the side wallsensors be fit in the vehicle chassis to improve the sensing accuracy.

However, the outputs from the acceleration sensors for sensing lateralcollisions are influenced by not only the collision impact but also thelateral movement of the vehicle chassis due to the lateral collisionetc. Depending on which longitudinal position on the vehicle the lateralcollision occurs, this influence may reduce the impact forces sensed bythe acceleration sensors. Consequently, the passenger protection systemmay not be able to be properly actuated.

For example, if a lateral collision occurs at a rear portion of thevehicle on a road surface having a low coefficient of friction, thevehicle is rotated angularly laterally in the lateral collisiondirection and may be rotated angularly to a considerable degree. If thecenter of rotation (spinning) is rear from the acceleration sensors,forces (acceleration) act on the sensors in the direction reverse to thecollision direction. After all, the rotation makes the outputs from theacceleration sensors lower than if the center of rotation is not rearfrom the sensors.

When a lateral collision occurs with the vehicle, the center of rotationof the vehicle is determined by the center of inertia mass (thelongitudinal center of gravity) of the vehicle and the positions of thefour tires, which resist the rotation of the vehicle. In general, when alateral collision occurs with the rear portion of the vehicle, thecenter of rotation is positioned longitudinally midway between the frontand rear tires.

SUMMARY OF THE INVENTION

In view of the foregoing problem, the object of the present invention isto provide a vehicular passenger protection system against lateralcollision that can accurately detect a lateral collision of the vehicleand protect passengers.

According to a first aspect of the present invention, a protectionsystem against lateral collision is provided for a vehicle. Theprotection system includes a first sensing section and a second sensingsection, which may be acceleration sensors, provided forward andrearward respectively of the rear end of a driver seat of the vehicle.The result of a calculation of outputs from the two sensors is the basisfor determining whether the vehicle has a lateral collision. Thecalculation is an operation of the value of a function. The parametersof the function may be analog or digital signals output from the sensorsand correlated to lateral force.

Alternatively, outputs from the sensors may be multilevel signals,combinations of which may be stored in advance in a map of thecombinations and function values. The combinations can be substitutedinto the map in order to find a function value. However, the logicaloperations of the binary signals of the outputs from the sensors areexcluded. Consequently, it is possible to selectively extract, from theforces developed by a lateral collision of the vehicle, the forcescorrelated to the value of the function of outputs from the two sensors,and to selectively attenuate the correlated forces. This makes itpossible to inhibit the vehicular lateral collision sensing accuracyfrom being lowered by the correlated forces.

In FIG. 1, a vehicle 1 is fit with a central acceleration sensor at apoint P and has a center of rotation M. The acceleration sensor senseslateral force (acceleration) acting on the vehicle. In general, thecenter of rotation of a vehicle is adjacent to the center of gravity ofthe vehicle. If a lateral collision occurs at point PO in a rightwarddirection on the vehicle 1, a component of force FO acts on the point POand rotates the vehicle angularly in the counterclockwise direction onthe center of rotation M. The lateral collision with the point POgexerts a force F1 in this direction on the point P. The rotation exertsa force F2 on the acceleration sensor at the point P in such a directionas to reduce the force F1. The resultant lateral force F acting on thepoint P decreases to F=F1−F2.

In FIG. 2, a vehicle 1 has a front acceleration sensor (first sensingsection) at a point P1 and a rear acceleration sensor (second sensingsection) at a point P2. If a lateral collision occurs at a rear portionof the vehicle, a force F4 is exerted in the collision direction on thepoint P2, and the vehicle is rotated counterclockwise around its centerof rotation M. The rotation exerts a force F3 on the point P2. Thelateral force acting on the front acceleration sensor at the point P1decreases to F=F1−F2, as described above. However, the lateral forceacting on the rear acceleration sensor at the point P2 increases to thesum of F3 and F4, that is, F=F3+F4.

Accordingly, by performing a calculation of outputs from the two sensingsections, it is possible to accurately sense the lateral collisionregardless of the rotation. In FIG. 2, if a lateral collision occurs atthe front portion of the vehicle, the clockwise rotation reduces theoutput from the rear acceleration sensor at the point P2, but increasesthe output from the front acceleration sensor at the point P1.Accordingly, it is possible to accurately sense the lateral collisionregardless of the rotation.

It is preferable that the first sensing section be forward of the rearend of the driver seat and positioned centrally between both right andleft sides of the vehicle. It is also preferable that the second sensingsection be rearward of the rear end of the driver seat and positionedcentrally between both right and left sides of the vehicle. Normally,this positions the center of rotation of the vehicle between the twosensing sections, so that the foregoing effect can be secured. Becausethe two sensing sections are positioned centrally between both lateralsides of the vehicle, it is possible to cope with lateral collisionsoccurring on either side. Because the two sensing sections are away fromthe doors of the vehicle, it is possible to sufficiently reduce themalfunction of the sensors that may be caused when the doors are openedand closed strongly.

It is furthermore preferable that the first sensing section includes aleft front sensor and a right front sensor, which are forward of therear end of the driver seat and adjacent to the left and right sidewalls respectively of the vehicle. It is also preferable that the secondsensing section includes a left rear sensor and a right rear sensor,which are rearward of the rear end of the driver seat and adjacent tothe left and right side walls respectively. This makes it possible toperform the calculation, with the sensors more sensitive to the lateralcollision.

The protection system against lateral collision might also include acenter front sensor and a center rear sensor that are positionedcentrally between both lateral sides of the vehicle and spaced apredetermined interval from each other longitudinally of the vehicle.For example, the average of outputs from the left front and right frontsensors approximates the output from the center front sensor. Likewise,the average of outputs from the left rear and right rear sensorsapproximates the output from the center rear sensor. Accordingly, byperforming a calculation of the two averages, it is possible to find acalculation result similar to that for the center front and center rearsensors.

It is furthermore preferable that the first sensing section includes aleft front sensor and a right front sensor, which are forward of therear end of the driver seat and adjacent to the left and right sidewalls respectively of the vehicle. It is also preferable that the secondsensing section includes a center rear sensor, which is rearward of therear end of the driver seat and positioned centrally between both sidesof the vehicle. For example, by using the average of outputs from theleft front and right front sensors, which are a pair of side wallsensors, it is possible to achieve an effect similar to that of thecenter front sensor, with the first sensing section more sensitive tolateral collisions. Likewise, the calculation might be performed withoutputs from a center front sensor, a left rear sensor and a right rearsensor.

It is furthermore preferable that the first sensing section includes aleft front sensor and a right front sensor, which are forward of therear end of the driver seat and adjacent to the left and right sidewalls respectively of the vehicle, and a center front sensor, which isforward of the rear end of the driver seat and positioned centrallybetween both sides of the vehicle. It is also preferable that the secondsensing section includes a center rear sensor, which is rearward of therear end of the driver seat and positioned centrally between both sidesof the vehicle. The degree of rotation may be sensed by the center frontand center rear sensors, which receive little door noise. The senseddegree can be the basis for correcting the outputs from the left frontand right front sensors, which are side wall sensors and more sensitiveto lateral collisions.

It is furthermore preferable that the first sensing section includes aleft front sensor and a right front sensor, which are forward of therear end of the driver seat and adjacent to the left and right sidewalls respectively of the vehicle, and a center front sensor, which isforward of the rear end of the driver seat and positioned centrallybetween both sides of the vehicle. It is also preferable that the secondsensing section includes a left rear sensor and a right rear sensor,which are rearward of the rear end of the driver seat and adjacent tothe left and right side walls respectively, and a center rear sensor,which is rearward of the rear end of the driver seat and positionedcentrally between both sides of the vehicle. The degree of rotation maybe sensed by the center front and center rear sensors, which receivelittle door noise. The sensed degree can be the basis for correcting theoutputs from the left front, right front, left rear and right rearsensors, which are side wall sensors and more sensitive to lateralcollisions.

Furthermore preferably, it should be determined that the vehicle has alateral collision if the output from either of the two sensing sectionsexceeds a predetermined threshold. This enables the protection system tocomprise a logical sum circuit for two comparison outputs, thussimplifying the circuit configuration. As described above, thedetermining section bases its determination on the result of acalculation of outputs from the two sensors forward and rearward of thedriver seat. Accordingly, the present invention bases the collisiondetermination on the logical sum of binary outputs from the first andsecond sensing sections, as well as the result of a calculation ofoutputs from the two sensors. The sensors for obtaining the results of acalculation and the logical sum of binary outputs may be or may not bethe same. The result of the calculation may be the basis for detectingthe degree of rotation, which may be the basis for changing thethreshold levels for the outputs from the first and second sensingsections. This calculation result may also be the basis for reducing theinfluence of rotation on the outputs from these sensing sections andbinarizing them.

Furthermore preferably, it should be determined whether the functionvalue exceeds a predetermined threshold, and the result of thedetermination should be the basis for determining whether the vehiclehas a lateral collision. This complicates the circuit configuration, butmakes the collision determination accurate by, for example, excludingthe influence of rotation more reliably, in comparison with theconventional system for sensing a lateral collision of a vehicle bysimply determining whether the output from one of the sensors of thesystem exceeds a threshold.

Furthermore preferably, it should be determined whether the differencebetween outputs from the first and second sensing sections exceeds apredetermined threshold, and the result of the determination should bethe basis for determining whether the vehicle has a lateral collision.As shown in FIG. 2, the difference (F3−F2) between the outputs from thetwo sensing sections is nearly twice F3. The occurrence of such rotationmeans a lateral collision with the rear portion of the vehicle and canbe the basis for determining that the vehicle has a lateral collision.Then, the passenger protection system of the vehicle may be actuated. Bycontrast, if the lateral collision does not angularly rotate thevehicle, the difference between the outputs from the two sensingsections is very small. This makes it evident that the differencebetween the outputs from the two sensors is the basis for fine detectionof rotation.

The lateral collisions with the rear portion can be distinguished fromthe other lateral collisions. Otherwise, the rotation caused by alateral collision can be distinguished from the vehicle displacementaccompanied by no rotation caused by a lateral collision. Accordingly,the actuating modes for passenger protection can be changed between acase where a lateral collision causes a great rotation and a case wherea lateral collision does not cause a great rotation. The actuating modesmay be combinations of airbags installed in different positions in thevehicle. This makes it possible to change the combinations of airbagsthat should be actuated in a case where the vehicle is angularly rotatedand a case where the vehicle is not angularly rotated.

Furthermore preferably, it should be determined whether the sum ofoutputs from the first and second sensing sections exceeds thethreshold, and the result of the determination should be the basis fordetermining whether the vehicle has a lateral collision. In this case,if the rotation reduces the output from one of the sensing sections andincreases the output from the other sensing section, it is possible toreduce the influence of the rotation on the output sum. This excludesthe influence of the rotation from the collision determination. Forexample, as shown in FIG. 2, the sum of the outputs from the two sensingsections is F1+F2+F3+F4. The acceleration forces F2 and F3 that therotation causes to act on the two acceleration sensors cancel eachother. As a result, the output sum is nearly twice F1, so that theinfluence of the rotation can be excluded. Besides, the output nearlydoubles, so that the SN ratio can be improved theoretically to a greatdegree in comparison with the conventional single-sensor type.

It is furthermore preferable that the function value be the basis forsubstantially changing the threshold. The result of the calculation ofthe outputs from the first and second sensing sections makes it possibleto detect the degree of rotation and change the collision determinationthreshold levels for the outputs from the first and second sensingsections for sensing lateral force. It is accordingly possible to reducethe detrimental influence of the rotation on the determination of themagnitude of lateral force. For example, the degree of rotation may bedetermined with the pair of front and rear sensors positioned centrallybetween both sides of the vehicle. The result of the determination maybe the basis for substantially changing the thresholds for the side wallsensors. The substantial change of each of these thresholds includeschanging it and correcting an output from the associated side wallsensor. The change of each threshold is equivalent to changing an outputfrom the associated sensing section, with the threshold kept constant.That is, the present invention involves changing the thresholds for thetwo sensing sections (acceleration sensors) by means of a function ofoutputs from the sensing sections. It is accordingly possible to reducethe influence of the rotation on the change of thresholds so that thethresholds can be properly changed.

In a preferred aspect of the present invention, the sensing sections forwhich the thresholds are changed are the acceleration sensors (side wallsensors) adjacent to both side walls of the vehicle. In this aspect, atleast two sensing sections that generate outputs for changing thethresholds are the acceleration sensors (central sensors) positionedcentrally between both sides of the vehicle. It is possible to inhibitthe outputs from the central sensors, which are little influenced by theopening and closing of the vehicle doors, from being varied with therotation.

In the meantime, the outputs from the central sensors are the basis forsubstantially changing the sensitivity of the side wall sensors.Accordingly, while the influence of the opening and closing of thevehicle doors can be excluded, the side wall sensors make it possible toreliably determine whether the vehicle has a lateral collision. Forexample, if the vehicle has no lateral collision, the outputs from thecentral sensors are the basis for increasing the thresholds for the sidewall sensors to reduce the determination sensitivity for them. Thisprevents it from being falsely determined that outputs from the sidewall sensors represent a lateral collision even when a door of thevehicle is closed.

By contrast, if the vehicle has a lateral collision, the outputs fromthe central sensors increase. The output increases are the basis forreducing the thresholds for the side wall sensors to increase thedetermination sensitivity for them. The increased sensitivity enablesquick determination of the lateral collision on the basis of the outputsfrom the side wall sensors. The central sensors are at least two innumber and spaced from each other longitudinally of the vehicle. Thethreshold control is based on the outputs from the central sensors.Accordingly, even if a lateral collision of the vehicle rotates itangularly, it is possible to reliably perform the threshold controlbased on the outputs from the central sensors that derive from therotation.

It is furthermore preferable that the difference between the outputsfrom the two sensing sections be the basis for substantially changingthe threshold. This makes it possible to well detect the degree ofrotation of the vehicle. That is, the rotation can be well detected asshown in FIG. 2 and stated earlier. For example, when the vehicle isangularly rotated, the thresholds for the side wall sensors may bereduced so that the foregoing effect can be well achieved.

It is alternatively preferable that the sum of the outputs from the twosensing sections be the basis for substantially changing the threshold.As shown in FIG. 2 and stated earlier, this makes it possible to welldetect the vehicle displacement independently of the rotation. When thevehicle is rotated angularly, this signal is the basis for reducing thethresholds for the side wall sensors to well achieve the foregoingeffect.

It is furthermore preferable that the result of a calculation of outputsfrom the center front and center rear sensors be the basis forsubstantially correcting outputs from the left front and right frontsensors. It should preferably be determined that the vehicle has alateral collision if either of the substantially corrected outputsexceeds a predetermined threshold. This enables the rotation to be wellsensed by the center front and center rear sensors, which receive littledoor noise. The signals from these two central sensors are the basis forexcluding the influence of the rotation on the side wall sensor signals,which have high sensitivity to the lateral collision of the vehicle, sothat the collision can be detected.

A protection system against lateral collision according to anotheraspect of the present invention includes a pair of sensors positionedcentrally between both sides of the body of a vehicle and spaced fromeach other longitudinally of the body. The outputs from the sensors arethe basis for detecting lateral collisions of the vehicle. The centrallypositioned sensors for sensing lateral force receive little door noise.Because one of the sensors can sense lateral collisions occurring onboth sides of the vehicle, the sensors can be fewer than theconventional side wall sensors.

It is preferable that the first and second sensing sections are locatedforward and rearward respectively of the longitudinal center of gravityof the vehicle. A lateral collision of the vehicle rotates it angularlyon a center near this center of gravity. Accordingly, the rotationcauses the two sensing sections to generate outputs in oppositedirections lateral of the vehicle. These outputs improve the detectionof rotation or better cancel each other.

It may be determined that the vehicle has a lateral collision if theoutput from either of the two sensing sections exceeds a predeterminedthreshold. This makes it possible to detect the lateral collisionaccurately without the influence of door noises.

The collision determination may be based on the result of a calculationof a predetermined function of outputs from the first and second sensingsections. As an example, if the collision determination is based on thecomparison between the sum of the outputs from the two sensing sectionsand a threshold, it is possible to reduce the influence of the rotationof the vehicle. As another example, the difference between the outputsfrom these sensing sections may be the basis for detecting the degree ofrotation, which may then be the basis for correcting the collisiondetermination.

The collision determination may be based on the result of acombinational operation of multistage signals output from the first andsecond sensing sections. In this case, because no analog signal from thetwo sensors is used, the circuit configuration and the operationprocessing can be simple.

The sensing section may further include a third sensing section adjacentto a side wall of the vehicle. An output from the third sensing sectionmay be substantially corrected with the result of the numeric orcombinational operation. It may be determined that the vehicle has alateral collision if the substantially corrected output exceeds apredetermined threshold. This makes it possible to finely determine thelateral collision without the influence of the rotation.

Outputs from the first and second sensing sections may be the basis forcomputing a signal positively correlated to the speed at which thevehicle is angularly rotated. The computed signal may be the basis forsubstantially correcting an output from the third sensing section. Itmay be determined that the vehicle has a lateral collision if theamplitude of the substantially corrected output exceeds a predeterminedthreshold. It is preferable that the third sensing section, which isadjacent to a side wall of the vehicle, be a side wall sensor forsensing lateral force. This makes it possible to accurately inhibit therotation in sensitive detection of a lateral collision of the vehicle.

It may be determined that the vehicle has a lateral collision if anoutput from either of the first and second sensing sections and anoutput from the third sensing section exceed the respective thresholds.It may also be determined that the vehicle has a lateral collision if apredetermined threshold is exceeded by the value of a function of anoutput from each of the first, second and third sensing sections.

This makes it possible to use each of the three sensors independentlyfor the detection of lateral collision, and to use the results of thecalculations of the outputs from these sensors. The calculation resultsmay be the basis for detecting a lateral collision of the vehicle whenthe vehicle is angularly rotated. If the output from each of the threesensing sections is very large, it is possible to determine a lateralcollision quickly without waiting for the determination delay caused bythe associated calculation.

A protection system against lateral collision according to a furtheraspect of the present invention includes a lateral force sensing sectionas included in the conventional protection system against lateralcollision. The protection system according to this aspect also includesan rotation sensing section for sensing the degree of rotation of avehicle, in addition to determining the output level of the lateralforce sensing section. Both the sensed level of lateral force and thelevel of rotation of the vehicle are the basis for determining whetherthe vehicle has a lateral collision. Consequently, the collisiondetermination is accurate regardless of the change of lateral force dueto the rotation.

It is preferable that an output from the lateral force sensing sectionbe the basis for substantially correcting an output from the rotationsensing section. It should preferably be determined that the vehicle hasa lateral collision if the substantially corrected output exceeds apredetermined threshold. This makes it possible to reduce the influenceof the rotation due to the lateral collision, by means of a simplestructure.

The rotation sensing section may include a plurality of the lateralforce sensing sections spaced from each other longitudinally of thevehicle. The determining section may detect the degree of rotation bymeans of a calculation of outputs from the lateral force sensingsections. Consequently, the rotation can be sensed by an accelerationsensor that can also function as the lateral force sensing section asstated already. This makes it possible to omit an exclusive sensor forsensing the rotation.

The rotation sensing section may include at least four sensing sectionsadjacent to both side walls of the vehicle and spaced predeterminedintervals longitudinally of the vehicle. In this case, the rotation canbe sensed by the side wall sensors that can sense the lateral collisionsensitively with little delay. This makes it possible to simplify thecircuit system.

The rotation sensing section may include a first sensing section and asecond sensing section, which are positioned centrally between bothsides of the vehicle and spaced a predetermined interval longitudinallyof the vehicle. This makes it possible to reduce the influence of doornoises and enables one sensor to sense the lateral collisions on bothsides so that the circuit system can be simpler.

The lateral force sensing sections may be adjacent to at least one ofboth side walls of the vehicle and spaced at predetermined intervalslongitudinally of the vehicle. This makes it possible to increase thesensitivity of the lateral force sensing sections for the determinationof lateral collision, reduce the delay and reduce the influence of doornoises when detecting the rotation.

The rotation sensing section may sense the rotation on the basis of thedifference between outputs from the lateral force sensing sectionsspaced from each other longitudinally of the vehicle. This makes itpossible to determine the level of rotation by means of a simpleoperation.

The longitudinal center of gravity of the vehicle may be positionedbetween the lateral force sensing sections spaced from each otherlongitudinally of the vehicle and forming the rotation sensing section.This makes it possible to improve the detectability of rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a schematic diagram of a sensing system, showing how a vehicleis rotated angularly by a lateral collision at a rear portion of thevehicle;

FIG. 2 is a schematic diagram of a sensing system according to thepresent invention, showing how a vehicle is rotated angularly by alateral collision at a rear portion of the vehicle;

FIG. 3 is a plan view of a vehicle, showing the arrangement ofacceleration sensors according to the first embodiment of the presentinvention;

FIG. 4 is a circuit diagram of the circuitry of the first embodiment;

FIG. 5 is a circuit diagram of the circuitry of the second embodiment ofthe present invention;

FIG. 6 is a circuit diagram of the circuitry of the third embodiment ofthe present invention;

FIG. 7 is a circuit diagram of the circuitry of the fourth embodiment ofthe present invention;

FIG. 8 is a circuit diagram of the circuitry of the fifth embodiment ofthe present invention;

FIG. 9 is a schematic diagram of the sixth embodiment of the presentinvention;

FIG. 10 is a schematic diagram of the seventh embodiment of the presentinvention;

FIG. 11 is a flowchart of the determination process in the seventhembodiment; and

FIG. 12 is a schematic diagram of the eighth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

Referring to FIG. 3, a vehicle 1 has a controller 2, a driver seat 3, amiddle seat 4, a rear seat 5, front side windows 6, middle side windows7 and rear side windows 8.

The vehicle 1 also has a left front acceleration sensor 11, a leftmiddle acceleration sensor 12, a left rear acceleration sensor 13, aright front acceleration sensor 14, a right middle acceleration sensor15, a right rear acceleration sensor 16, a center front accelerationsensor 17 and a center rear acceleration sensor 18, which overlapsvertically with the middle seat 4. Each of the left and right frontacceleration sensors 11 and 14 is positioned between the adjacent frontand middle side windows 6 and 7. The left middle acceleration sensor 12is positioned roughly between the adjacent middle and rear side windows7 and 8. The left rear acceleration sensor 13 is roughly rearward of theadjacent rear side window 8. The acceleration sensors 11–16 are sidewall sensors. The acceleration sensors 17 and 18 are central sensors.The acceleration sensors 11–18 sense the lateral acceleration of thevehicle 1.

The controller 2 in this embodiment will be described below withreference to FIG. 4. For the sake of simplicity, the signal processingin the side wall sensors 14–16, which is identical with that in the sidewall sensors 11–13, will not be described.

In FIG. 4, the acceleration sensors 11–18 output analog signal voltagesnearly proportional to the lateral acceleration of the vehicle 1. Theanalog signal voltages output from the acceleration sensors 11–13, 17and 18 are amplified and integrated by operational amplifiers 21–23, 24and 25 for voltage amplification and integration, respectively. Insteadof being integrated, the voltages might be processed by low-passfilters.

The analog signal voltages output from the operational amplifiers 21–23are compared with threshold voltages Vth1, Vth2 and Vth3 by comparators41–43, respectively, which output binary voltages through an OR circuit50 and a power amplifier (not shown) to an airbag device 60 or anotherpassenger protection device. If the analog signal voltage input intoeach of the comparators 41–43 is higher than the associated thresholdvoltage Vth, the level of the associated binary voltage is high.

The analog signal voltages output from the operational amplifiers 24 and25 undergo subtraction through an operational amplifier 31 for analogsubtraction. The voltage output from the operational amplifier 31 iscompared with a threshold voltage Vth4 by a comparator 44, which outputsa binary voltage through the OR circuit 50 and the power amplifier (notshown) to the airbag device 60. The level of this binary voltage is highif the voltage output from the operational amplifier 31 is higher thanthe threshold voltage Vth4. It is obvious that the analog subtractionmight be replaced by digital subtraction.

Thus, the output from each of the side wall sensors 11–16 is comparedwith the threshold Vth, and the difference between the outputs from thecentral sensors 17 and 18 is extracted and compared with the thresholdVth. The comparison of the output difference is the basis fordetermining whether the vehicle 1 is rotated angularly to a greatdegree. If the vehicle 1 is rotated angularly beyond a certain degreedefined by the threshold Vth4, it is determined that the vehicle has alateral collision. Consequently, even if a lateral collision rotates thevehicle 1 angularly to a great degree, the passengers in the vehicle canbe protected.

(Second Embodiment)

The controller 2 in this embodiment will be described below withreference to FIG. 5. For the sake of simplicity, the signal processingin the side wall sensors 14–16 will not be described.

This embodiment differs from the first embodiment shown in FIG. 4 inhaving an operational amplifier 32 for analog addition in place of theoperational amplifier 31 for analog subtraction.

In FIG. 5, the analog signal voltages output from the operationalamplifiers 24 and 25 are added together by the operational amplifier 32.The voltage output from the operational amplifier 32 is compared with athreshold voltage Vth5 by the comparator 44, which outputs a binaryvoltage through the OR circuit 50 and the power amplifier (not shown) tothe airbag device 60. The level of this binary voltage is high if thevoltage output from the operational amplifier 32 is higher than thethreshold voltage Vth5.

Thus, in this embodiment, the output from each of the side wall sensors11–16 is compared with a threshold Vth5, and the sum of the outputs fromthe central sensors 17 and 18 is extracted and compared with thethreshold Vth5. The comparison of the sum of the outputs is the basisfor finding a lateral force less influenced by the rotation of thevehicle. It is then determined whether the lateral force is large ornot. This makes it possible to determine whether the vehicle has alateral collision, while suppressing the influence of the rotation.

Consequently, even if the rear portion of the vehicle has a lateralcollision, which angularly rotates the vehicle, decreasing the analogsignal voltage output from the central sensor 17, the rotation hardlyinfluences the sum of the analog signal voltages from the centralsensors 17 and 18. This makes it possible to determine whether thevehicle has a lateral collision, thereby protecting the vehiclepassengers.

(Third Embodiment)

The controller 2 in this embodiment will be described below withreference to FIG. 6.

This embodiment differs from the first embodiment shown in FIG. 4 inhaving a threshold setting circuit 70 for variably setting the thresholdvoltages Vth1, Vth2 and Vth3 in amplitude depending on the level of theoutput from the comparator 44.

The threshold voltages Vth1, Vth2 and Vth3 are generated by a thresholdvoltage generator (not shown) and changed in amplitude into high or lowlevels by the threshold setting circuit 70. For example, a DC offsetvoltage may be added to each of the threshold voltages Vth1, Vth2 andVth3 input from the threshold voltage generators. Alternatively, thethreshold voltage generators might generate three pairs of high-leveland low-level threshold voltages so that the threshold setting circuit70 could select one of the high-level and low-level voltages of eachpair as one of the threshold voltages Vth1, Vth2 and Vth3.

In this embodiment, if the central sensors 17 and 18 sense a lateralcollision, the comparator 44 outputs a high-level voltage, which lowersthe threshold voltages Vth1, Vth2 and Vth3 of the comparator 44. Thisenables the comparators 41–44 to sensitively detect the lateralcollision on the basis of the outputs from the side wall sensors 11–13.When a door of the vehicle is closed, the outputs from the centralsensors 17 and 18 are still low, and the output from the operationalamplifier 31 for analog subtraction is low. Accordingly, the comparator44 outputs a low-level voltage, which causes the threshold settingcircuit 70 to set the threshold voltages Vth1, Vth2 and Vth3 high. Thiscauses the comparators 41–44 to output low-level voltages, which preventthe actuation of the airbag device 60.

Thus, in this embodiment, the difference between the outputs from thecentral sensors 17 and 18 is the basis for changing the thresholdvoltages Vth1, Vth2 and Vth3 for the side wall sensors. Accordingly, theoutput difference is the basis for well sensing the rotation caused by alateral collision at the rear portion of the vehicle, and the thresholdvoltages Vth1, Vth2 and Vth3 are changed to the low levels.Consequently, even if the lateral collision lowers the outputs from theside wall sensors, the rotation does not lower the lateral collisionsensitivity of these sensors, because the thresholds as well can belowered.

(Fourth Embodiment)

The controller 2 in this embodiment will be described below withreference to FIG. 7.

This embodiment differs from the third embodiment shown in FIG. 6 inhaving the operational amplifier 32 for analog addition in place of theoperational amplifier 31 for analog subtraction.

In FIG. 7, the analog signal voltages output from the operationalamplifiers 24 and 25 are added together by the operational amplifier 32.The voltage output from the operational amplifier 32 is compared withthe threshold voltage Vth5 by the comparator 44, which outputs a binaryvoltage to the threshold setting circuit 70. The level of this binaryvoltage is high if the voltage output from the operational amplifier 32is higher than the threshold voltage Vth5.

Thus, in this embodiment, the sum of the outputs from the centralsensors 17 and 18 is the basis for changing the threshold voltages Vth1,Vth2 and Vth3 for the side wall sensors 11–16. The sum of the outputs ishardly affected by the rotation caused by a lateral collision of a rearportion of the vehicle. Only when this sum is large, the thresholdsVth1, Vth2, Vth3 for the side wall sensors can be lowered. When a doorof the vehicle is closed, the central sensors 17 and 18 sense a lateralforce that attenuates greatly relative to the lateral collision. Even inthis case, because the sum of the outputs from the central sensors 17and 18 is small, the thresholds for the side wall sensors 11–16 arestill held high.

By contrast, when the vehicle has a lateral collision, the sum of theoutputs from the central sensors 17 and 18 is large, and consequentlythe thresholds for the side wall sensors 11–16 are lowered. This enablesthe side wall sensors 11–16 to sensitively sense the lateral collision.Even if the vehicle is angularly rotated, the rotation exerts only areduced influence on the sum of the outputs from the central sensors 17and 18. Accordingly, it is also possible to reduce the influence of therotation on the change of the thresholds for the side wall sensors11–16. After all, while inhibiting the influence of rotation, it ispossible to accurately determine whether the vehicle has a lateralcollision.

(Fifth Embodiment)

The controller 2 in this embodiment will be described below withreference to FIG. 8.

This embodiment differs from the third embodiment shown in FIG. 6 inhaving an A-D converter 80 in place of the comparator 44 and a thresholdsetting circuit 70, which can perform calculations in it, in place ofthe threshold setting circuit 70 of FIG. 6.

The operational amplifiers 24 and 25 output analog signal voltages,which undergo subtraction through the operational amplifier 31. Theoutput from this operational amplifier 31 is converted into a digitalsignal by the A-D converter 80. Accordingly, the digital signalrepresents the difference between the outputs from the center frontsensor 17 and center rear sensor 18. As described above, this outputdifference includes many signal components that link with rotation. Inthis embodiment, the thresholds for the side wall sensors 11–13 arechanged in series depending on the amplitude of the digital signal,which correlates greatly to rotation.

If a lateral collision occurs at the rear portion of the left side wallof the vehicle and angularly rotates the vehicle, as shown in FIG. 1,the rotation differently influences the outputs from the side wallsensors 11–13 in longitudinally different positions. Specifically, therotation increases the output from the left rear sensor 13, exertslittle influence on the left middle sensor 12 and reduces the outputfrom the left front sensor 11.

If a lateral collision occurs at the rear portion of the left side wallof the vehicle and angularly rotates the vehicle, forces act on thecenter front sensor 17 and the center rear sensor 18 as shown in FIG. 2.In this case, on the assumption that the voltage output from the centerrear sensor 18 is positive (+), the difference between the outputs fromthe central sensors 17 and 18 is F3+F4−F1+F2, which is a positively highvalue. Accordingly, if the output difference is positively high, it isnecessary to increase the threshold Vth3 for the left rear sensor 13 inproportion to the difference and reducing the threshold Vth1 for theleft front sensor 11, without changing the threshold Vth2 for the leftmiddle sensor 12. This makes it possible to cancel the increase in theoutput from the left rear sensor 13 and the decrease in the output fromthe left front sensor 11 due to the rotation.

This is similar to a case where a lateral collision occurs at the frontportion of the left side wall, or at a rear or front portion of theright side wall of the vehicle, thereby angularly displacing thevehicle. Similarly, it is necessary to proportionally change thethresholds for the right front sensor 14 and the right rear sensor 16.

Thus, in this embodiment, different threshold changes are made becauseoutput variations due to the rotation differ between the front and rearside wall sensors. This makes it possible to determine more accurately,independently of the rotation, whether the vehicle has a lateralcollision.

(Sixth Embodiment)

This embodiment excludes central sensors 17 and 18 and uses only sidewall sensors 11, 13, 14 and 16. Of course, this embodiment might alsouse side wall sensors 12 and 15.

This embodiment will be described with reference to FIG. 9 in a casewhere a lateral collision occurs at the rear portion of the left sidewall of the vehicle. The outputs from the acceleration sensors 11, 13,14 and 16 include lateral components f11, f13, f14 and f16,respectively, and components y11, y13, y14 and y16, respectively,resulting from the rotation.

The sum of the outputs from the left front sensor 11 and the right frontsensor 14 would approximate the output from the center front sensor 17.The sum of the outputs from the left rear sensor 13 and the right rearsensor 16 would approximate the output from the center rear sensor 18.The sum of the outputs from the left rear sensor 13 and the right rearsensor 16 is subtracted from the sum of the outputs from the left frontsensor 11 and the right front sensor 14, with a first remainder. Theoutput from the center rear sensor 18 would be subtracted from theoutput from the center front sensor 17, with a second remainder, whichis an output influenced greatly by the rotation. Because the tworemainders approximate each other, the first remainder is the basis fordetermining how much the vehicle is angularly rotated.

Likewise, the sum of the outputs from all of the side wall sensors 11,13, 14 and 16 would approximate the sum of the outputs from the centralsensors 17 and 18, which is an output influenced little by the rotation.The substitution of these outputs for the difference between and the sumof the outputs from the central sensors 17 and 18 in the first throughfifth embodiments can produce effects similar to those in thoseembodiments.

(Seventh Embodiment)

This embodiment excludes side wall sensors 11–16 and uses only centralsensors 17 and 18.

This embodiment will be described with reference to FIG. 10 in a casewhere a lateral collision occurs at the rear portion of the left sidewall of the vehicle. The outputs from the acceleration sensors 17 and 18include lateral components f17 and f18, respectively. The outputs alsoincludes components y17 and y18, respectively, resulting from therotation.

As described above, the difference between the outputs from the centralsensors 17 and 18 includes a large amount of lateral force resultingfrom the rotation component. Accordingly, by using this outputdifference (ΔV) as the basis for changing the threshold Vth for thecentral sensors 17 and 18, it is possible to reduce the influence of therotation on the outputs from these sensors 17 and 18. The rotationlittle influences the sum of the outputs from the central sensors 17 and18. Accordingly, by comparing this output sum with the threshold, it islikewise possible to determine whether the vehicle has a lateralcollision, while inhibiting the influence of the rotation.

The influence of the rotation due to the lateral collision at the rearportion of the left side wall is exerted in such directions as to reducethe output V17 from the center front sensor 17 and increase the outputV18 from the center rear sensor 18. Accordingly, by reducing thethreshold Vth17 for the center front sensor 17 and increasing thethreshold Vth18 for the center rear sensor 18, depending on theamplitude of the difference between the outputs from these sensors 17and 18, it is possible to determine whether the vehicle has a lateralcollision, independently by means of each sensor while inhibiting theinfluence of the rotation.

Similar operations are represented by the flowchart shown in FIG. 11. Inthis operation, outputs V17 and V18 of the sensors 17 and 18 arecorrected instead of changing thresholds Vth17 and Vth18. Specifically,the outputs V17 and V18 of the center sensors 17 and 18 are read at step101. The outputs V17 and V18 are compared with the respective thresholdsVth17 and Vth18 at step 102. If the outputs are larger than thethresholds, the outputs V17 and V18 are added and subtracted at step103. Then the outputs V17 and V18 are corrected by the difference(ΔV=V17−V18) at step 104. For instance, the outputs V17 and V18 areincreased and decreased in proportion to the difference ΔV,respectively. The corrected outputs V17, V18 and the sum of the outputsare compared with respective thresholds at step 105. Then, at step 106,it is determined whether any one of the corrected V17, V18 and sum islarger than the respective threshold. If YES, a lateral collision isdetected at step 107, and the airbag 60 is actuated at step 108. It isobvious that this flowchart can be replaced by hardware circuitry, as isthe case with the other embodiments.

(Eighth Embodiment)

This embodiment is shown in FIG. 12 and differs from the firstembodiment in excluding the left rear sensor 13 and the right rearsensor 16. The control operation in this embodiment is similar to thearithmetic or operational determination processes in the first throughfifth embodiments. However, the determination process for the side wallsensors 13 and 16 is omitted.

Instead, it is possible to carry out lateral collision determination bymeans of the center rear sensor 18 by computing the difference betweenthe outputs from the central sensors 17 and 18 to find a signalinfluenced greatly by rotation, and correcting the output from or thethreshold for the center rear sensor 18 depending on the amplitude ofthis signal. This makes it possible to reduce the number of accelerationsensors and the influence of rotation on lateral collisiondetermination.

In each of the embodiments, it is assumed that the center of rotation,which is the longitudinal center of gravity, of the vehicle ispositioned always between the central sensors 17 and 18. However, thepositions of the engine etc. may shift the center front sensor 17rearward of the center of rotation of the vehicle having a lateralcollision. This reduces the component included in the difference betweenthe outputs from the central sensors 17 and 18 and resulting from therotation. Accordingly, it is preferable that the center front sensor 17be positioned as forward as possible so that the center of rotation canbe positioned between the central sensors 17 and 18, most preferably atthe middle point between them.

In each of the embodiments, the thresholds for the comparison with theoutputs for lateral collision determination are changed or correcteddepending on how much the vehicle is angularly rotated. Alternatively,with the thresholds fixed, the outputs might be corrected.

In the additive and subtractive operations, the input signals might beweighted. The signals might be classified in different levels.Combinations of the signal levels and outputs might be stored in advancein the form of a map. Outputs could be obtained by substituting thelevels of the input signals into the map.

In each of the embodiments, the acceleration sensors sense the rotation.Alternatively, the rotation might be sensed by exclusive rotationsensors. The outputs from the lateral force sensors could be correctedwith the outputs from the rotation sensors.

1. A protection system against lateral collision for a vehicle includinga driver seat and a passenger protecting device for protecting apassenger against a lateral collision, the protection system comprising:a sensing section for sensing a magnitude of an electric signalrepresenting a physical quantity correlated to a lateral force exertedon the vehicle when the vehicle has a lateral collision, wherein thesensing section includes a first sensing section provided forward of arear end of the driver seat and a second sensing section providedrearward of the rear end of the driver seat; a determining section fordetermining that the vehicle has the lateral collision if the sensedmagnitude of the electric signal exceeds a predetermined threshold,wherein the determining section is constructed to perform a calculationby substituting outputs from the first and second sensing sections forthe variables of a predetermined function that are outputs as non-binarysignals from the first and second sensing sections, and wherein thedetermining section is further constructed to use a function value thatis a result of the calculation as a basis for determining whether thevehicle has the lateral collision; and a controlling section forcommanding actuation of the passenger protecting device if thedetermining section determines that the vehicle has a lateral collision,wherein the determining section determines whether the function valueexceeds a predetermined threshold; wherein the determining section usesthe result of the determination as a basis for determining whether thevehicle has a lateral collision, wherein the determining sectiondetermines whether a difference between outputs from the first andsecond sensing sections exceeds a predetermined threshold, and whereinthe determining section uses a result of the determination as a basisfor determining whether the vehicle has a lateral collision.
 2. Aprotection system against lateral collision for a vehicle including adriver seat and a passenger protecting device for protecting a passengeragainst a lateral collision, the protection system comprising: a sensingsection for sensing a magnitude of an electric signal representing aphysical quantity correlated to a lateral force exerted on the vehiclewhen the vehicle has a lateral collision, wherein the sensing sectionincludes a first sensing section provided forward of a rear end of thedriver seat and a second sensing section provided rearward of the rearend of the driver seat; a determining section for determining that thevehicle has the lateral collision if the sensed magnitude of theelectric signal exceeds a predetermined threshold, wherein thedetermining section is constructed to perform a calculation bysubstituting outputs from the first and second sensing sections for thevariables of a predetermined function that are outputs as non-binarysignals from the first and second sensing sections, and wherein thedetermining section is further constructed to use a function value thatis a result of the calculation as a basis for determining whether thevehicle has the lateral collision; and a controlling section forcommanding actuation of the passenger protecting device if thedetermining section determines that the vehicle has a lateral collisionwherein the determining section determines whether the function valueexceeds a predetermined threshold; wherein the determining section usesthe result of the determination as a basis for determining whether thevehicle has a lateral collision, wherein the determining sectiondetermines whether a sum of outputs from the first and second sensingsections exceeds a threshold, and wherein the determining section uses aresult of the determination as a basis for determining whether thevehicle has a lateral collision.
 3. A protection system against lateralcollision for a vehicle including a driver seat and a passengerprotecting device for protecting a passenger against a lateralcollision, the protection system comprising: a sensing section forsensing a magnitude of an electric signal representing a physicalquantity correlated to a lateral force exerted on the vehicle when thevehicle has a lateral collision, wherein the sensing section includes afirst sensing section provided forward of a rear end of the driver seatand a second sensing section provided rearward of the rear end of thedriver seat; a determining section for determining that the vehicle hasthe lateral collision if the sensed magnitude of the electric signalexceeds a predetermined threshold, wherein the determining section isconstructed to perform a calculation by substituting outputs from thefirst and second sensing sections for the variables of a predeterminedfunction that are outputs as non-binary signals from the first andsecond sensing sections, and wherein the determining section is furtherconstructed to use a function value that is a result of the calculationas a basis for determining whether the vehicle has the lateralcollision; and a controlling section for commanding actuation of thepassenger protecting device if the determining section determines thatthe vehicle has a lateral collision, wherein the determining sectiondetermines that the vehicle has a lateral collision if an output fromeither of the two sensing sections exceeds a predetermined threshold,wherein the determining section substantially changes the threshold onthe basis of the function value, and wherein the determining sectionsubstantially changes the threshold on the basis of a difference betweenthe outputs from the first and second sensing sections.
 4. A protectionsystem against lateral collision for a vehicle including a driver seatand a passenger protecting device for protecting a passenger against alateral collision, the protection system comprising: a sensing sectionfor sensing a magnitude of an electric signal representing a physicalquantity correlated to a lateral force exerted on the vehicle when thevehicle has a lateral collision, wherein the sensing section includes afirst sensing section provided forward of a rear end of the driver seatand a second sensing section provided rearward of the rear end of thedriver seat; a determining section for determining that the vehicle hasthe lateral collision if the sensed magnitude of the electric signalexceeds a predetermined threshold, wherein the determining section isconstructed to perform a calculation by substituting outputs from thefirst and second sensing sections for the variables of a predeterminedfunction that are outputs as non-binary signals from the first andsecond sensing sections, and wherein the determining section is furtherconstructed to use a function value that is a result of the calculationas a basis for determining whether the vehicle has the lateralcollision; and a controlling section for commanding actuation of thepassenger protecting device if the determining section determines thatthe vehicle has a lateral collision, wherein the determining sectiondetermines that the vehicle has a lateral collision if an output fromeither of the two sensing sections exceeds a predetermined threshold,wherein the determining section substantially changes the threshold onthe basis of the function value, and wherein the determining sectionsubstantially changes the threshold on the basis of a sum of the outputsfrom the first and second sensing sections.
 5. A protection systemagainst lateral collision for a vehicle including a driver seat and apassenger protecting device for protecting a passenger against a lateralcollision, the protection system comprising: a sensing section forsensing a magnitude of an electric signal representing a physicalquantity correlated to a lateral force exerted on the vehicle when thevehicle has a lateral collision, wherein the sensing section includes afirst sensing section provided forward of a rear end of the driver seatand a second sensing section provided rearward of the rear end of thedriver seat; a determining section for determining that the vehicle hasthe lateral collision if the sensed magnitude of the electric signalexceeds a predetermined threshold, wherein the determining section isconstructed to perform a calculation by substituting outputs from thefirst and second sensing sections for the variables of a predeterminedfunction that are outputs as non-binary signals from the first andsecond sensing sections, and wherein the determining section is furtherconstructed to use a function value that is a result of the calculationas a basis for determining whether the vehicle has the lateralcollision; and a controlling section for commanding actuation of thepassenger protecting device if the determining section determines thatthe vehicle has a lateral collision, wherein the first sensing section,which is forward of the rear end of the driver seat, includes a leftfront sensor and a right front sensor that are adjacent to the left andright side walls respectively of the vehicle and a center front sensorpositioned centrally between both lateral sides of the vehicle, whereinthe second sensing section, which is rearward of the rear end of thedriver seat, includes a center rear sensor positioned centrally betweenboth lateral sides of the vehicle, wherein the determining sectionsubstantially corrects the outputs from the left front and right frontsensors on a basis of a result of a calculation of outputs from thecenter front and center rear sensors, and wherein the determiningsection determines that the vehicle has a lateral collision if either ofthe substantially corrected outputs exceeds a predetermined threshold.6. A protection system against lateral collision for a vehicle includinga passenger protecting device for protecting a passenger against alateral collision, the protection system comprising: a sensing sectionfor sensing a magnitude of an electric signal representing a physicalquantity correlated to a lateral force exerted on the vehicle when thevehicle has the lateral collision, wherein the sensing section includesa first sensing section and a second sensing section that are positionedcentrally between both lateral sides of the vehicle, the first sensingsection being forward and spaced a predetermined interval from thesecond sensing section; a determining section for determining on a basisof the sensed magnitude of the electric signal that the vehicle has thelateral collision, wherein the sensed quantity includes at least outputsfrom the first and second sensing sections; and a controlling sectionfor commanding an actuation of the passenger protecting device if thedetermining section determines that the vehicle has the lateralcollision, wherein the determining section performs a calculation of apredetermined function of outputs from the first and second sensingsections, and uses the result of the calculation as the basis fordetermining whether the vehicle has a lateral collision, wherein thesensing section further includes a third sensing section adjacent to alateral side wall of the vehicle, and wherein the determining sectionsubstantially corrects an output from the third sensing section with acalculation result and determines that the vehicle has a lateralcollision if a substantially corrected output exceeds a predeterminedthreshold.
 7. The protection system against lateral collision accordingto claim 6, wherein the determining section uses outputs from the firstand second sensing sections as a basis for computing a signal correlatedto a speed at which the vehicle is angularly rotated, uses the computedsignal as the basis for substantially correcting an output from thethird sensing section, and determines that the vehicle has a lateralcollision if a magnitude of the substantially corrected output exceeds apredetermined threshold.
 8. The protection system against lateralcollision according to claim 6, wherein the determining sectiondetermines that the vehicle has a lateral collision if an output fromeither of the first and second sensing sections and an output from thethird sensing section exceed the respective thresholds, performs acalculation by substituting an output from each of the first, second andthird sensing sections in a predetermined function to find a functionvalue, and determines that the vehicle has a lateral collision if thefunction value exceeds a predetermined threshold.
 9. A protection systemagainst lateral collision for a vehicle including a passenger protectingdevice for protecting a passenger against a lateral collision, theprotection system comprising: a lateral force sensing section forsensing a lateral force exerted on the vehicle when the vehicle has thelateral collision; a rotation sensing section for sensing a rotation ofthe vehicle in which a vehicle front part and a vehicle rear part movein opposite lateral directions; a determining section for using outputsfrom the two sensing sections as a basis for determining whether thevehicle has the lateral collision; and a controlling section forcommanding actuation of the passenger protecting device if thedetermining section determines that the vehicle has the lateralcollision, wherein the determining section substantially corrects anoutput from the rotation sensing section on a basis of an output fromthe lateral force sensing section, and determines that the vehicle has alateral collision if the substantially corrected output exceeds apredetermined threshold.
 10. The protection system against lateralcollision according to claim 9, wherein the rotation sensing sectionincludes a plurality of the lateral force sensing sections spaced fromeach other longitudinally of the vehicle, and wherein the determiningsection detects a degree of rotation by means of a calculation ofoutputs from the lateral force sensing sections.
 11. The protectionsystem against lateral collision according to claim 10, wherein therotation sensing section includes at least four sensing sectionsadjacent to both lateral side walls of the vehicle and spacedpredetermined intervals longitudinally of the vehicle.
 12. Theprotection system against lateral collision according to claim 10,wherein the rotation sensing section includes a first sensing sectionand a second sensing section that are positioned centrally between bothlateral sides of the vehicle and spaced a predetermined intervallongitudinally of the vehicle.
 13. The protection system against lateralcollision according to claim 12, wherein the lateral force sensingsections are adjacent to at least one of both lateral side walls of thevehicle and spaced predetermined intervals longitudinally of thevehicle.
 14. The protection system against lateral collision accordingto claim 10, wherein the lateral force sensing sections forming therotation sensing section are spaced from each other longitudinally ofthe vehicle with respect to a longitudinal center of gravity of thevehicle.
 15. The protection system against lateral collision for avehicle including a passenger protecting device for protecting apassenger against a lateral collision, the protection system comprising:a lateral force sensing section for sensing a lateral force exerted onthe vehicle when the vehicle has the lateral collision; a rotationsensing section for sensing a rotation of the vehicle; a determiningsection for using outputs from the two sensing sections as a basis fordetermining whether the vehicle has the lateral collision; and acontrolling section for commanding actuation of the passenger protectingdevice if the determining section determines that the vehicle has thelateral collision, wherein the determining section substantiallycorrects an output from the rotation sensing section on a basis of anoutput from the lateral force sensing section, and determines that thevehicle has a lateral collision if the substantially corrected outputexceeds a predetermined threshold.
 16. A protection system againstlateral collision for a vehicle including a passenger protecting devicefor protecting a passenger against a lateral collision, the protectionsystem comprising: a lateral force sensing section for sensing a lateralforce exerted on the vehicle when the vehicle has the lateral collision;a rotation sensing section for sensing a rotation of the vehicle; adetermining section for using outputs from the two sensing sections as abasis for determining whether the vehicle has the lateral collision; anda controlling section for commanding actuation of the passengerprotecting device if the determining section determines that the vehiclehas the lateral collision, wherein the rotation sensing section includesa plurality of the lateral force sensing sections spaced from each otherlongitudinally of the vehicle, wherein the determining section detects adegree of rotation by means of a calculation of outputs from the lateralforce sensing sections, and wherein the rotation sensing section sensesthe rotation on a basis of a difference between outputs from the lateralforce sensing sections spaced from each other longitudinally of thevehicle.